Lever apparatuses have been generally used in a mechanical field such as machine tools and industrial machines and widely used as force transmitting parts of movable mechanisms in various other structures. As shown in FIGS. 1A and 1B, in such a lever apparatus, a force point c is provided at one end of a lever member a axially supported by a fulcrum b fixed on the ground G. The lever member a is pivoted by means of a crank arm g connected to a driving wheel f, so that a work force is generated at an action point d.
In the conventional lever apparatus, since the lever member a is axially supported on the fixed fulcrum b, the loci of both the force point c and the action point d draw arcs upon pivotal movement of the lever member a. Even if a vertical force acts on the force point c, as shown in FIG. 1A, this force cannot be applied along a single straight line. This problem is also posed at the action point d. For this reason, in the conventional lever apparatus, in order to convert linear motion of the force point c into pivotal motion of the lever member a or convert pivotal motion of the lever member a into linear motion at the action point d, a force point regulator as a combination of an elongated hole Lc and a roller Rc and an action point regulator as a combination of an elongated hole Ld and a roller Rd, as shown in FIG. 1A, are used at portions of the force point c and the action point d, respectively. Ranges W of motion to be converted are determined by the lengths of the elongated holes Lc and Ld, respectively, and the ranges W cannot be increased due to limitations of mechanical strength. As far as the force transmission magnitudes are concerned, distances A1 and B1 from the fulcrum b to the force and action points c and d are changed upon pivotal movement of the lever member a, and a transmission force is undesirably changed.
A torsion stress is produced at the action point d upon pivotal movement of the lever member a by a pivot angle .alpha. in a direction indicated by an arrow in FIG. 1B. Therefore, a force cannot be effectively transmitted.
In an example shown in FIG. 2, when a force is to act at a point c to shift an action point d downward, an upper portion of an action point link member g is distorted in a direction to be bent as indicated by a dotted line. As a result, a left portion of an upper end and a right portion of a lower end of a guide hole of a support guide member i are worn out.